Semiconductor

NEET Physics · 93 questions · Page 2 of 10 · Click an option or "Show Solution" to reveal answer

Q11

A full wave rectifier circuit consists of two p-n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output?

A p-n junction diodes

B Capacitor

C Load resistance

D A centre-tapped transformer

Correct Answer

Option B

Solution

Capacitor used to remove AC ripples from Rectifier output.

Q12

For the following logic circuit, the truth table is:

A <table class=tg style=undefined;table-layout: fixed; width: 164px> <colgroup> <col style=width: 55px> <col style=width: 54px> <col style=width: 55px> </colgroup> <thead> <tr> <th class=tg-baqh>A</th> <th class=tg-baqh>B</th> <th class=tg-baqh>Y</th> </tr> </thead> <tbody> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> </tbody> </table>

B <table class=tg style=undefined;table-layout: fixed; width: 164px> <colgroup> <col style=width: 55px> <col style=width: 54px> <col style=width: 55px> </colgroup> <thead> <tr> <th class=tg-baqh>A</th> <th class=tg-baqh>B</th> <th class=tg-baqh>Y</th> </tr> </thead> <tbody> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> </tr> </tbody> </table>

C <table class=tg style=undefined;table-layout: fixed; width: 164px> <colgroup> <col style=width: 55px> <col style=width: 54px> <col style=width: 55px> </colgroup> <thead> <tr> <th class=tg-baqh>A</th> <th class=tg-baqh>B</th> <th class=tg-baqh>Y</th> </tr> </thead> <tbody> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> </tbody> </table>

D <table class=tg style=undefined;table-layout: fixed; width: 164px> <colgroup> <col style=width: 55px> <col style=width: 54px> <col style=width: 55px> </colgroup> <thead> <tr> <th class=tg-baqh>A</th> <th class=tg-baqh>B</th> <th class=tg-baqh>Y</th> </tr> </thead> <tbody> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> </tr> </tbody> </table>

Correct Answer

Option A

Solution

<p>

y=\overline{\overline{\mathrm{A}} \cdot \overline{\mathrm{B}}}=\overline{\overline{\mathrm{A}}}+\overline{\overline{\mathrm{B}}}

</p> <p>

=(\mathrm{A}+\mathrm{B}) ~\mathrm{OR}

Gate</p> <p> <table class=tg style=undefined;table-layout: fixed; width: 164px> <colgroup> <col style=width: 55px> <col style=width: 54px> <col style=width: 55px> </colgroup> <thead> <tr> <th class=tg-baqh>A</th> <th class=tg-baqh>B</th> <th class=tg-baqh>Y</th> </tr> </thead> <tbody> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> <td class=tg-baqh>0</td> </tr> <tr> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>0</td> <td class=tg-baqh>1</td> </tr> <tr> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> <td class=tg-baqh>1</td> </tr> </tbody> </table></p>

Q13

The incorrect statement about the property of a Zener diode is :

A p and n regions of Zener diode are heavily doped

B Zener voltage remains constant at breakdown

C It is designed to operate under reverse bias

D Depletion region formed is very wide

Correct Answer

Option D

Solution

Zener diode is special purpose p-n junction diode, which is generally operated in reverse bias for its operation of voltage regulation.

It is a heavily doped p-n junction.

Due to large doping concentration depletion width is narrower.

Q14

The collector current in a common base amplifier using n-p-n transistor is 24 mA. If 80% of the electrons released by the emitter is accepted by the collector, then the base current is numerically :

A 3 mA and entering the base

B 6 mA and leaving the base

C 3 mA and leaving the base

D 6 mA and entering the base

Correct Answer

Option D

Solution

Given

{I_C} = 24

\alpha = 0.8 = {{{I_C}} \over {{I_E}}}

{I_E} = {{24} \over {0.8}}

= 30

{I_B} = {I_E} - {I_C} = 30 - 24

= 6

mA, entering the base

Q15

As the temperature increases, the electrical resistance

A Increases for both conductors and semiconductors

B Decreases for both conductors and semiconductors

C Increases for conductors but decreases for semiconductors

D Decreases for conductors but increases for semiconductors

Correct Answer

Option C

Solution

As the temperature increases the resistivity of the conductor increases hence the electrical resistance increases.

However for semiconductor the resistivity decreases with the temperature.

Hence electrical resistance of semiconductor decreases.

Q16

In half wave rectification, if the input frequency is 60 Hz, then the output frequency would be

A Zero

B 30 Hz

C 60 Hz

D 120 Hz

Correct Answer

Option C

Solution

In half wave rectifier, the output frequency is same as that of input frequency.

Q17

Consider the following statements (A) and (B) and identify the correct answer. (A) A Zener diode is connected in reverse bias, when used as a voltage regulator. (B) The potential barrier of p-n junction lies between 0.1 V to 0.3 V.

A (A) is incorrect but (B) is correct.

B (A) and (B) both are correct.

C (A) and (B) both are incorrect.

D (A) is correct and (B) is incorrect.

Correct Answer

Option D

Solution

In reverse biased, after breakdown, voltage across the zener diode becomes constant.

Therefore zener diode is connected in reverse biased when used as voltage regulator. for Ge Potential barrier V 0 = 0.3 V Si Potential barrier V 0 = 0.7 V

Q18

The electron concentration in an n-type semiconductor is the same as hole concentration in a p-type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them.

A No current will flow in p-type, current will only flow in n-type

B Current in n-type = current in p-type

C current in p-type > current in n-type

D current in n-type > current in p-type

Correct Answer

Option D

Solution

In N type semiconductor majority charge carriers are e $-$ and P type semiconductor majority charge carriers are holes.

I = neAV d = neA ( $\mu$ E) As $\mu$ e > $\mu$ h $\Rightarrow$ I e > I h

Q19

For transistor action, which of the following statements is correct ?

A Base, emitter and collector regions should have same size.

B Both emitter junction as well as the collector junction are forwarded biased.

C The base region must be very thin and lightly doped.

D Base, emitter and collector regions should have same doping concentrations.

Correct Answer

Option C

Solution

For transistor action, the input is always forward biased and output is always reverse biased.

For this Base has to be very thin and lightly doped.

Q20

The increase in the width of the depletion region in a p-n junction diode is due to :

A reverse bias only

B both forward bias and reverse bias

C increase in forward current

D forward bias only

Correct Answer

Option A

Solution

The width of depletion layer will increase with reverse bias.

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